Can anyone identify this stuff and suggest how I might kill it? Its a green-brown growth, slippery and slimy, somewhat resembles seaweed. When it dries it turns black and goes quite crispy. It gets raked up frequently but just comes back again.

This edible revolting muck is usually found in gravel driveways, and can form large icky drifts if unchecked. You can control it, but never fully eradicate it. The smallest flake will multiply like crazy once it gets moisture. Flakes will get stuck in tyres and shoes, grass verges, etc.

I have found spraying with cheap homebrand bleach will work, but takes a month or two to break it down. If you leave it for a few minutes, it will show any spots you have missed, as the bleach will lighten the mould.

I did use an algaecide / moss killer with good results, but seems more difficult to locate these days.

My thoughts are no longer my own and is probably representative of our media-controlled government

I have found spraying with cheap homebrand bleach will work, but takes a month or two to break it down. If you leave it for a few minutes, it will show any spots you have missed, as the bleach will lighten the mould.

I did use an algaecide / moss killer with good results, but seems more difficult to locate these days.

Do you recall what strength you used the bleach at? I was thinking of getting some cheap swimming pool chlorine and making a solution from that but no idea what strength to use.

Make the copper solution up at 2 to 3 times the recommended conc. Note that copper is quite bad if it gets into waterways so don't use it when rain is expected and don't dispose of any used solution down the drain.

I have found spraying with cheap homebrand bleach will work, but takes a month or two to break it down. If you leave it for a few minutes, it will show any spots you have missed, as the bleach will lighten the mould.

I did use an algaecide / moss killer with good results, but seems more difficult to locate these days.

Do you recall what strength you used the bleach at? I was thinking of getting some cheap swimming pool chlorine and making a solution from that but no idea what strength to use.

There's two types of 30 Seconds cleaner - one is sodium hypchlorite based and the other is benzylkonium chloride which is an algicide. If you read the side of the container, it will tell you the concentration of bleach they use, its probably on their website somewhere too. Then you can choose your own source of bleach and dilute to suit.